Measuring-tool.



C. A. HIRTH.

MEASURING TOOL.

-APPucmoN mso 1AN.|4, |913.

Patented Nov. 30, 1915.

UMTED STATES PATENT ore-ion CARL ALBERT HIRTH, OF CANNSTATT-S'IUTTGART, GERMANY, ASSGNGR TD FBTUNA WERKE ALBERT HIRTH, OF CANNSTA'.IlT-S'FUJJTGARE,l GERMANY, A' CQRFB-ATION F GERMANY.

Specication of Letters vPatent.

MEASURINGTOOL This invention relates to an improved,

meansuring tool for accurately determining the diameter of hollow bodies or' bores in which contact-bodies, such as balls, are employed and held in contact with the object the interior diameter` of which is to be measured.

Measuring tools for accurately determining the interior diameter of bodies, which are provided vvith balls as intermediate contact-bodies, and into which a conicallytapering mandrel is inserted, were used heretofore. 'The size of the axial shiftingmotion of the mandrel was read oli' 0n a scale which was arranged on the mandrel, by meansof an index-point or a reading-ofedge on the supporting frame, and thereby the diameter of the hollow object to be measured ascer-` tained. ln measuringl tools of this kind, the

diameter to be determined was heretofore l obtained in a fairly accurate manner by the axial shifting of the mandrel, but the measurements were not very reliable inasmuch as the shifting of the mandrel could not be read olf with suiiicient clearness and exactitude from the graduation-lines of the scale, inasmuch as the latter were covered to some extent by the reading-olf edge of the frame. The unavoidable separating space which was formed between the mandrel and the reading-ofi' edge' affected likewise the read- Aby the correctness of the measurements increased to a heretofore unattained degree of accuracy without the addition of any new and sensitive parts.

The invention consists of a measuring tool in which the mandrel, instead of being eonicallytapering shape, is made in cylin- Patented Nov. 3ft, 1915.

ders arranged step-shaped or in steps one next to the other, atthat portion which is used for measuring the diameter of :he objects, vvhich cylinders'differ in diameter but little, according to the degree of exactness required for the tool.v in connection with they cylindrical steps of the measuring portion of the mandrel the graduation-lines of the scale formerly used on the scale-portion of the mandrel are now extended into cylinders or zones of more or less width, so that the reading ofi' of the measurements, even with a slightly inaccurate adjustment of the index-point or reading-oft' edge, does not impair the accuracy of the measurements.

The accompanying drawing represents a.

vertical central section of one embodiment o'f my improved measuring tool, showing it as used for determining thek diameter of a race in the guide-ring of a ball-bearing of any .approved construction.

ln the improved measuring tool 'contacti bodies are used, preferably the same steel balls c which are used in the ball-bearing itself. Three or more of these balls are inserted into the'race Against the .iinished face d of the ring a is placed the face of a supporting'frame f having a guide-ring i into which is inserted the cylindrical portion or shank h1 of the axiaily-shiftable mandrel m, while the step-shaped measuring portion k of thesame is pushed through between the balls c, so that the latter are forced in outward direction 4and by the inti mate contact of the halls@ with the race b of the ring a the free axial shifting of the mandrel is prevented. The edge 2' on the rear face of the ring-shaped guide g of the supper-tino' frame f forms then the edge for reading off the measure for the diameter of the race b.

,- According to the present invention the measuring portion la of the mandrel, which is introduced between the balls c, divided into a plurality-of cylindrical steps' r", r3, 113, rf, 1', the diameters of which diter little from each other., according 'to the degree of correctness required the easureznent, increasing, for instance, ll t. one. from the other. 7h-en the racen a s, for

the balls c shown in the draw' however, ,he shifted rd t ward for the width of the Winner-step :at without instance,

W .ndre can,

fait

changing the diametrical` distance of the balls c as they iride on the cylindrical step of the mandrel. The cylindrical portion or shank h1 of the mandrel is notl provided with graduation-lines, but subdivided into graduating zones s1, s2, 83, 8*, 85 of the same Width as the steps 1" to 1'5 of the cylinder l1., and on these zones the measurements indicated by the steps `of the measuring portion h are placed in such manner as to be easily read off the graduated zones of the shank h1, which forms the scale of; the instrument.

As thev numbers of the measurements are clearly placed on the graduated zones, they can be read ofi even under unfavorable conditions, that is, when by the least possible shifting of the mandrel the reading-ofi` edge 'a' should be slightly moved over the graduated zone s* or even onto the zone si. For this reason, as for example in the simple arrangement descrbed, deviations up to 1 mm. and more of the distance of the racecenter from the face (l do not produce any noticeable error in the measurement of the racediameter, even when carried out, for ex ample, kto, lan exactness or correctness of 1/100 of' a millimeter.

In addition to the cylindrically-stepped portion h of the mandrel, a conically-tapering end-portion fr with a corresponding scale or zone s on the cylindrical portion or shank of the mandrel can be used for a preliminary measuring of the diameter. y

It is advisable to support the balls c, which are used as the contact-bodies', in a cage t of the supporting frame so that these balls, While possessing a free play in lateral direction. are prevented from dropping out of the frame when the measuring instrument is not in 'use by the inwardly-projecting inner embracing edge of the cage t, which is of spe Iial importance, as they'are thereby re-l tained. inposition at the proper equal distance from each other around the stepshaped mea airing portion L, that is to say, with three balls at an angle of 120 from each other.

I claim:

l. In a measuring tool for determining the internal diameter, a mandrel provided adjacent one end with a plurality of measuring cylinders, oney adjacent the other, and

adapted for measuring the diameter of the objects, each cylinder differing from its adjacent cylinder but little in diameter, said mandrel being also provided with a .scaleportion adjacent the other end having graduations forming zones corresponding in width to thc length of the measuring cylinders, and means supporting the balls to be measured, contacting with certain portions of the mandrel, and'extending therefrom to corresponding portions of the scale portion.

2. A measuringtool, comprising a mandrel provided adjacent one end with a plurality of cylinders of dill'erent diameters and adapted for measuring the dialneter of the objects, the cylinder of smallest diameter being at one end of the' mandrel and each successive cylinder being slightly largerin diameter, said mandrel being provided with a guide or scale adjacent the other end of the mandrel having graduations, and a supporting frame provided at one end with contact-balls moving over the several measuring cylinders for determining the diameter of the object to be measured and having its other'end extend over to the scale-portion and provided 'ith m xans for reading oil' the measurements on the scale-portion.

3. In a measuring tool, the combination of a 'mandrel provided adjacent one end with a plurality of cylinders and adapted for measuring the diameter of the objects, the diameter of each successive cylinder varying from the diameter of the adjacent cylinder a verv small amount,said mandrel being provided with a cylindrical guide or scale portion adjacent the other end of the mandrel, and having graduations forming zones equal in width to the lengthv of the cylinders, a guide-frame provided at one end with a ring-shaped portion having contact-balls moving over the measuring cylinders, and a guide-ring connected 'with the guide-frame and extending around the scale-portion and provided with a reading-off edge.

In testimony, that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses.

I CARL ALBERT HIRTH.

lvitnesses PAULINE MLLER, Fun. KLAIBER.

Copies of this patent may be obtained for uve cents each, by addressing the Commissioner of Patents.

Washington, D. C. 

